Arbitrary and reconfigurable optical vortex generation: a high-efficiency technique using director-varying liquid crystal fork gratings

Abstract

A high-efficiency technique for optical vortex (OV) generation is proposed and demonstrated. The technique is based on liquid crystal fork gratings with space-variant azimuthal orientations, which are locally controlled via polarization-sensitive alignment layers. Thanks to the optical rewritability of the alignment agent and the dynamic image generation of the digital micro-mirror device, fork gratings can be instantly and arbitrarily reconfigured. Corresponding optical vortices carrying arbitrary azimuthal and radial indices are demonstrated with a conversion efficiency of 98.5%, exhibiting features of polarization control and electrical switching. The technique may pave a bright road toward OV generation, manipulation, and detection.

Intense harmonics generation with customized photon frequency and optical vortex

“…Different values of l mean that the photon has different vortex characteristics and carries different OAMs. Owing to the limitation of the etching resolution, it is difficult to obtain a vortex beam of high topological charge through conventional methods such as forked diffraction gratings [18,19] or spiral phase plates [15]. There have been some efforts, such as the use of a helical undulator [20][21][22], Compton backscattering effects [23,24], and high-order harmonics generation (HHG) [25][26][27][28], devoted to generating a light beam with OAM.…”

Ultrabroadband gradient-pitch Bragg-Berry mirrors

“…Of course, although present results are restricted to the polychromatic management of the orbital angular mo-mentum of light, they could be extended to any phase shaping by appropriate surface patterning of alignment layers using state-of-the-art techniques [3,4]. Nevertheless, it should be recalled that light scattering remains a challenging issue that need further work.…”

“…However, the realization of lossless scalable geometric phase metasurfaces operating in the visible domain remains technologically difficult. In practice, promising developments came from patterned liquid crystals technologies where the possibility to achieve arbitrary twodimensional orientational patterns ψ 2D (x, y) [3,4] can be endowed with an additional degree of freedom along the third dimension, namely, ψ 3D (x, y, z).…”

Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

“…In this work, we introduce a gradient blazed phase into the vortex phase, and propose a THz LC element named forked polarization grating (FPG) [30,31]. The specifically designed LC directors with gradient rotation are implemented using photoalignment technology.…”